The invention relates generally to a method for forming dielectric/insulating oxide film, and more particularly to a method for fabricating a Strontium-Tantalum-Oxide thin film.
A structure of dielectric/insulating oxide film is used in various fields. For example, it is used in i) an insulating film of an NDRO-type ferroelectric memory device which has a structure of Metal-film/Ferroelectric-film/Insulating-film/Silicon, ii) a gate oxide film substituting for silicon oxide film, and iii) an insulating film of Electro Luminescent Display (ELD) device, and the like.
A development of ferroelectric semiconductor devices for the high-capacity memory has been actively made to overcome the refresh problem related to the conventional Dynamic Random Access Memory (DRAM), by using capacitors made of ferroelectric materials. The ferroelectric memory device is a kind of non-volatile memory device. Since it has merits of keeping the stored data under power-off state and being equivalent to the conventional DRAM in the operating speed, it is viewed as the memory device for next-generation. The ferroelectric material in a normal temperature has several hundreds to several thousand of dielectric constants, and it has states of two stable remnant polarizations. Therefore, since polarization directions of input signals are controlled toward toe directions of the applied electric field, when the applied electric field is removed, digital signals 0 and 1 are stored on the basis of directions of the remaining remanent polarization.
Until now, dielectric-films in ferroelectric capacitors generally use PZT (Pb(ZrxTi1xe2x88x92x)O3), SBT (SrxBiyTa2O9), and the like. The important features of each material are as follows: the PZT has merits that its ferroelectric characteristics are excellent, and it allows a low-temperature process essentially needed for fabricating high-density devices. Meanwhile, due to the fatigue phenomenon, it has demerits that the specific oxide electrode should be used, and the leakage-current is large. Contrary to the PZT, since the SBT shows no fatigue phenomenon, and has distinguished characteristics on metal electrode, developments of the SBT have been actively made.
Also, intermediate insulting-films used in the ferroelectric memory device must have the important features as follows: high dielectric constant, low leakage-current, and no reaction with the ferroelectric insulating-films and silicon surfaces. In addition, gate oxide films substituting for silicon oxide films, and insulating-films of Electro Luminescent Display (ELD) device require the high dielectric constant and the low leakage-current as well.
The present invention overcomes the above conventional problems and provides a method for forming, at low temperature, Strontium-Tantalum-Oxide film with a comparative high dielectric-constant and a comparative low leakage-current.
In order to accomplish the above, according to the present invention, a method is provided for forming Strontium-Tantalum-Oxide thin film on a patterned substrate comprising the steps of:
a) arranging said substrate in a reaction chamber;
b) introducing a source material into the reaction chamber using a carrier gas, said source material being vaporized in said carrier gas and containing Strontium Tantalum Ethoxide;
c) blowing said source material out of said reaction chamber using purge gas;
d) introducing oxygen gas into the reaction chamber and generating oxygen plasma; and
e) blowing the oxygen plasma out of the reaction chamber using purge gas.
Further, according to the present invention, an apparatus for forming Strontium-Tantalum-Oxide thin film on a patterned substrate comprising:
a) a reaction chamber for accommodating said substrate;
b) a source supplying unit for supplying a source material to the reaction chamber using a carrier gas, said source material being vaporized in said carrier gas and containing Strontium Tantalum Ethoxide;
c) an oxygen supplying unit for introducing oxygen gas into the reaction chamber;
d) a plasma generating unit for generating oxygen plasma in the reaction chamber; and
e) a purge gas injecting unit for injecting purge gas into the reaction chamber.
The present invention provide a method for forming Strontium-Tantalum-Oxide (Srxe2x80x94Taxe2x80x94O) thin films, and it provides a structure of device using the formed thin films. The present invention forms the Strontium-Tantalum-Oxide films using an atomic layer deposition, and embodies structures for i) an insulating film of an NDRO-type ferroelectric memory device that has a structure of Metal-film/Ferroelectric-film/Insulating-film/Silicon, ii) a gate oxide film substituting for a silicon oxide film, and iii) an insulating film of Electro Luminescent Display (ELD) device. In the Strontium-Tantalum-Oxide films, a composition ratio of Sr/Ta is within a range of 0.45 to 0.60.